Bottom Line:
This senescent phenotype was mediated by 4-hydroxnonenal (4-HNE), a lipid peroxidation product secreted from foam cells; scavenging of 4-HNE in the co-culture medium blunted this effect.Molecular manipulation of TXNIP expression confirmed its involvement in foam cell-induced senescence.Collectively, these findings suggest that foam cell-released 4-HNE activates PPARδ in VEC, leading to increased TXNIP expression and consequently to senescence.

fig03: Scavenging of 4-HNE reduces the expression of senescence markers in VEC co-cultured with foam cells. THP-1 monocytes seeded in transwell inserts were transformed to foam cells (FC) as described under legend to Figure1A, and then co-cultured with VEC for 72 hrs, in the absence or presence of 10 mM FL-926-A16, with daily addition of the scavenger. At the end of the incubation period, the cells were harvested, lysed and processed for Western blotting as described under the legend to Figure1B. Shown are representative Western blots and quantification of the various senescence markers. Results are expressed as mean ± SEM, n = 3; *P < 0.05 for differences from the untreated cultures.

Mentions:
To further confirm this suggestion, we investigated whether the scavenging of 4-HNE in the transwell system could blunt foam cell-induced VEC senescence. FL-926-A16 is a potent scavenger of bioactive aldehydes, including 4-HNE (European Patent EP 2519507 B1, US Patent 8623900 B2 and 57). Unlike the natural scavenger, L-carnosine, which is degraded by carnosinase in human cells 58, its alcohol derivative FL-926-A16 is resistant to degradation. LC-MS/MS analysis of culture medium from control (PMA-treated) macrophages and foam cells exposed to FL-926-A16 showed that the latter covalently bound 4-HNE (Fig. S2). Interestingly, this analysis also revealed that, in addition to 4-HNE, foam cells secreted glyoxal, methyl glyoxal and acrolein, which were also scavenged by FL-926-A16. When added to the medium of the co-culture system, FL-926-A16 reduced the level of p16 and p21 and increased p-pRB level (Fig.3), supporting the suggestion that the scavenged molecules, including 4-HNE, induce senescence.

fig03: Scavenging of 4-HNE reduces the expression of senescence markers in VEC co-cultured with foam cells. THP-1 monocytes seeded in transwell inserts were transformed to foam cells (FC) as described under legend to Figure1A, and then co-cultured with VEC for 72 hrs, in the absence or presence of 10 mM FL-926-A16, with daily addition of the scavenger. At the end of the incubation period, the cells were harvested, lysed and processed for Western blotting as described under the legend to Figure1B. Shown are representative Western blots and quantification of the various senescence markers. Results are expressed as mean ± SEM, n = 3; *P < 0.05 for differences from the untreated cultures.

Mentions:
To further confirm this suggestion, we investigated whether the scavenging of 4-HNE in the transwell system could blunt foam cell-induced VEC senescence. FL-926-A16 is a potent scavenger of bioactive aldehydes, including 4-HNE (European Patent EP 2519507 B1, US Patent 8623900 B2 and 57). Unlike the natural scavenger, L-carnosine, which is degraded by carnosinase in human cells 58, its alcohol derivative FL-926-A16 is resistant to degradation. LC-MS/MS analysis of culture medium from control (PMA-treated) macrophages and foam cells exposed to FL-926-A16 showed that the latter covalently bound 4-HNE (Fig. S2). Interestingly, this analysis also revealed that, in addition to 4-HNE, foam cells secreted glyoxal, methyl glyoxal and acrolein, which were also scavenged by FL-926-A16. When added to the medium of the co-culture system, FL-926-A16 reduced the level of p16 and p21 and increased p-pRB level (Fig.3), supporting the suggestion that the scavenged molecules, including 4-HNE, induce senescence.

Bottom Line:
This senescent phenotype was mediated by 4-hydroxnonenal (4-HNE), a lipid peroxidation product secreted from foam cells; scavenging of 4-HNE in the co-culture medium blunted this effect.Molecular manipulation of TXNIP expression confirmed its involvement in foam cell-induced senescence.Collectively, these findings suggest that foam cell-released 4-HNE activates PPARδ in VEC, leading to increased TXNIP expression and consequently to senescence.